Outdoor unit of air conditioner and air conditioner

ABSTRACT

An outdoor unit of an air conditioner includes: an outdoor heat exchanger provided with a plurality of refrigerant paths including a flow rate-variable refrigerant path; an ambient air temperature detector that detects an ambient air temperature; and a controller that decreases a flow rate of a refrigerant flowing into the flow rate-variable refrigerant path in a case where the ambient air temperature detected by the ambient air temperature detector is equal to or higher than a threshold ambient air temperature as compared to a case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2015-015121 filed with the Japan Patent Office on Jan. 29, 2015, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

Embodiments of the present disclosure relate to an outdoor unit of an air conditioner including a heat exchanger with a plurality of refrigerant paths, and an air conditioner.

2. Description of the Related Art

For a known air conditioner, an outdoor unit includes an outdoor heat exchanger with a plurality of refrigerant paths vertically disposed in parallel, for example. When the air conditioner performs heating operation, the outdoor heat exchanger serves as an evaporator. Accordingly, a refrigerant brought into a gas-liquid two-phase state or a liquid state in an indoor unit flows into the outdoor heat exchanger. At that time, the liquid refrigerant flows biased toward the lower refrigerant paths under the influence of gravity. This may cause reduction in heating capacity due to degradation in evaporating performance of the outdoor heat exchanger.

There has been proposed a method for correcting the bias in the flow rate of the refrigerant among a plurality of refrigerant paths as described below (for example, refer to JP-A 2011-232011). According to this method, capillary tube is provided in each of the refrigerant paths of the outdoor heat exchanger. The flow passage resistance of the capillary tube in a specific refrigerant path is set to be higher than the flow passage resistances of the capillary tubes in the other refrigerant paths. At the outdoor heat exchanger as described above, for example, the flow passage resistance of the capillary tube in the lower refrigerant path is set to be higher than the flow passage resistances of the capillary tubes in the other refrigerant paths. In this case, when the outdoor heat exchanger serves as an evaporator, the amount of the liquid refrigerant flowing into the lower path is regulated by the capillary tube. This corrects the bias in the flow rate of the refrigerant among the refrigerant paths. Accordingly, it is possible to suppress degradation in evaporating performance of the outdoor heat exchanger, thereby preventing reduction in heating capacity.

SUMMARY

An outdoor unit of an air conditioner includes: an outdoor heat exchanger provided with a plurality of refrigerant paths including a flow rate-variable refrigerant path; an ambient air temperature detector that detects an ambient air temperature; and a controller that decreases a flow rate of a refrigerant flowing into the flow rate-variable refrigerant path in a case where the ambient air temperature detected by the ambient air temperature detector is equal to or higher than a threshold ambient air temperature as compared to a case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of a refrigerant circuit in an air conditioner according to an embodiment of the present disclosure, and FIG. 1B is a block diagram of an outdoor unit controller in the air conditioner;

FIG. 2A is a diagram illustrating a flow rate balancer in the embodiment of the present disclosure in the state where an open/close valve is open, and FIG. 2B is a diagram illustrating the flow rate balancer in the state where the open/close valve is closed; and

FIG. 3 is a flowchart of a process performed by the outdoor unit controller in the embodiment of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

Reduction in heating capacity of the air conditioner due to decrease in the circulation volume of a refrigerant during heating operation becomes larger at lower ambient air temperatures. In particular, when the ambient air temperature is extremely low (for example, lower than −15° C.), heating capacity may decrease significantly even with a slight decrease in the circulation volume of refrigerant. This is because, in the outdoor heat exchanger serving as an evaporator, the refrigerant is more unlikely to draw heat from the ambient air at lower ambient air temperatures, and thus the evaporating performance degrades significantly even with a slight decrease in refrigerant flow rate.

In the outdoor heat exchanger described in JP-A 2011-232011, the flow passage resistance of the capillary tube provided in each of the refrigerant paths decrease the circulation volume of refrigerant. Accordingly, when the ambient air temperature is extremely low, the heating capacity may decrease largely due to the significant degradation in the evaporating performance of the outdoor heat exchanger.

An object of the present disclosure is to provide an outdoor unit of an air conditioner. The outdoor unit can suppress degradation in air conditioning performance resulting from decrease in the circulation volume of refrigerant at lower ambient air temperatures while correcting the bias in the flow rate of the refrigerant among the refrigerant paths.

An outdoor unit of an air conditioner according to one aspect of the present disclosure includes: an outdoor heat exchanger provided with a plurality of refrigerant paths including a flow rate-variable refrigerant path; an ambient air temperature detector that detects an ambient air temperature; and a controller that decreases a flow rate of a refrigerant flowing into the flow rate-variable refrigerant path in a case where the ambient air temperature detected by the ambient air temperature detector is equal to or higher than a threshold ambient air temperature as compared to a case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.

In the above described outdoor unit of an air conditioner, a controller decreases a flow rate of a refrigerant flowing into the flow rate-variable refrigerant path in a case where the ambient air temperature detected by the ambient air temperature detector is equal to or higher than a threshold ambient air temperature as compared to a case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator. Consequently, the outdoor unit can suppress degradation in air conditioning performance resulting from decrease in the circulation volume of refrigerant at lower ambient air temperatures while correcting the bias in the flow rate of the refrigerant among the refrigerant paths.

The embodiment of the present disclosure will be described below in detail with reference to the accompanying drawings. In the air conditioner according to this embodiment, three indoor units are coupled in parallel to one outdoor unit. Using all the indoor units simultaneously can perform cooling operation or heating operation. However, the mode of the present disclosure is not limited to the following embodiment. The mode of the present disclosure can be modified in various manners without deviating from the gist of the present disclosure.

EXAMPLE

As illustrated in FIG. 1A, an air conditioner 1 in this embodiment includes one outdoor unit 2 and three indoor units 5 a to 5 c. The indoor units 5 a to 5 c are coupled in parallel to the outdoor unit 2 via pipes including a first liquid pipe 8 a, a second liquid pipe 8 b, a third liquid pipe 8 c, and a gas pipe 9. That is, the air conditioner 1 includes the outdoor unit 2, the indoor units 5 a to 5 c, and the pipes coupling the outdoor unit 2 to the indoor units 5 a to 5 c.

The foregoing components are coupled in a manner as described below. One end of the first liquid pipe 8 a is coupled to a first liquid-side closing valve 27 a of the outdoor unit 2. The other end of the first liquid pipe 8 a is coupled to a liquid pipe coupling portion 53 a of the indoor unit 5 a. One end of the second liquid pipe 8 b is coupled to a second liquid-side closing valve 27 b of the outdoor unit 2. The other end of the second liquid pipe 8 b is coupled to a liquid pipe coupling portion 53 b of the indoor unit 5 b. One end of the third liquid pipe 8 c is coupled to a third liquid-side closing valve 27 c of the outdoor unit 2. The other end of the third liquid pipe 8 c is coupled to a liquid pipe coupling portion 53 c of the indoor unit 5 c.

One end of the gas pipe 9 is coupled to a gas-side closing valve 28 of the outdoor unit 2. The other end of the gas pipe 9 is branched in three, and the gas pipe 9 has three other ends. The three other ends of the gas pipe 9 are coupled to respective gas pipe coupling portions 54 a to 54 c of the indoor units 5 a to 5 c. In this manner, the outdoor unit 2 is couple to the indoor units 5 a to 5 c via the first liquid pipe 8 a, the second liquid pipe 8 b, the third liquid pipe 8 c, and the gas pipe 9. These components constitutes a refrigerant circuit 10 in the air conditioner 1.

The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, a first expansion valve 24 a, a second expansion valve 24 b, a third expansion valve 24 c, an accumulator 25, a first flow rate balancer 26 a, a second flow rate balancer 26 b, a third flow rate balancer 26 c, the first liquid-side closing valve 27 a, the second liquid-side closing valve 27 b, the third liquid-side closing valve 27 c, the gas-side closing valve 28, an outdoor fan 29, and an outdoor unit controller 200. These members except for the outdoor fan 29 and the outdoor unit controller 200 are mutually coupled via refrigerant pipes described later in detail to constitute an outdoor unit refrigerant circuit 20 as part of the refrigerant circuit 10.

The compressor 21 is a capacity-variable compressor. That is, the compressor 21 is driven by a motor not illustrated controlled in rotation speed by an inverter. Accordingly, the operating capacity of the compressor 21 is variable. The refrigerant discharge opening of the compressor 21 is coupled to a port a of the four-way valve 22 described later via a discharge pipe 41. The refrigerant intake side of the compressor 21 is coupled to the refrigerant outflow side of the accumulator 25 via an intake pipe 42.

The four-way valve 22 is a valve for switching the directions in which the refrigerant flows. The four-way valve 22 includes four ports a, b, c, and d. The port a is coupled to the refrigerant discharge opening of the compressor 21 via the discharge pipe 41. The port b is coupled to each one end of first to seventh refrigerant paths 23 a to 23 g included in the outdoor heat exchanger 23 described later via a refrigerant pipe 43. The port c is coupled to the refrigerant inflow side of the accumulator 25 via a refrigerant pipe 46. The port d is coupled to the gas-side closing valve 28 via an outdoor unit gas pipe 45.

The outdoor heat exchanger 23 exchanges heat between the refrigerant and the ambient air taken into the outdoor unit 2 from an inlet not illustrated by rotation of the outdoor fan 29 described later. The outdoor heat exchanger 23 has the first refrigerant path 23 a, the second refrigerant path 23 b, the third refrigerant path 23 c, the fourth refrigerant path 23 d, the fifth refrigerant path 23 e, the sixth refrigerant path 23 f, and the seventh refrigerant path 23 g. These seven refrigerant paths are vertically disposed in parallel in order of the first refrigerant path 23 a, the second refrigerant path 23 b, , and the seventh refrigerant path 23 g from the bottom. As described above, one end of each of the first refrigerant path 23 a to the seventh refrigerant path 23 g is coupled to the port b of the four-way valve 22 via the refrigerant pipe 43. The other end of each of the first refrigerant path 23 a to the seventh refrigerant path 23 g is coupled to one end of each of a first liquid branch pipe 44 a to a third liquid branch pipe 44 c via an outdoor unit liquid pipe 44. The outdoor heat exchanger 23 serves as a condenser when the refrigerant circuit 10 is in a cooling cycle and serves as an evaporator when the refrigerant circuit 10 is in a heating cycle.

The first expansion valve 24 a is provided in the first liquid branch pipe 44 a. One end of the first liquid branch pipe 44 a is coupled to the outdoor unit liquid pipe 44, and the other end of the same is coupled to the first liquid-side closing valve 27 a. The second expansion valve 24 b is provided in the second liquid branch pipe 44 b. One end of the second liquid branch pipe 44 b is coupled to the outdoor unit liquid pipe 44, and the other end of the same is coupled to the second liquid-side closing valve 27 b. The third expansion valve 24 c is provided in the third liquid branch pipe 44 c. One end of the third liquid branch pipe 44 c is coupled to the outdoor unit liquid pipe 44, and the other end of the same is coupled to the third liquid-side closing valve 27 c.

The degrees of opening of the first expansion valve 24 a, the second expansion valve 24 b, and the third expansion valve 24 c are controlled by the outdoor unit controller 200. By controlling the degree of opening of the first expansion valve 24 a, the flow rate of the refrigerant flowing into the indoor unit 5 a is adjusted. By controlling the degree of opening of the second expansion valve 24 b, the flow rate of the refrigerant flowing into the indoor unit 5 b is adjusted. By controlling the degree of opening of the third expansion valve 24 c, the flow rate of the refrigerant flowing into the indoor unit 5 c is adjusted. The first expansion valve 24 a, the second expansion valve 24 b, and the third expansion valve 24 c are electronic expansion valves driven by a pulse motor not illustrated. The degrees of opening of the first expansion valve 24 a, the second expansion valve 24 b, and the third expansion valve 24 c are adjusted according to the number of pulses given by the pulse motor.

As described above, the refrigerant inflow side of the accumulator 25 is coupled to the port c of the four-way valve 22 via the refrigerant pipe 46. The refrigerant outflow side of the accumulator 25 is coupled to the refrigerant suction opening of the compressor 21 via the intake pipe 42. The accumulator 25 separates the refrigerant flowing therein into a gas refrigerant and a liquid refrigerant to send the gas refrigerant to the compressor 21.

The first flow rate balancer 26 a is provided in the first refrigerant path (flow rate-variable refrigerant path) 23 a at the four-way valve 22 side. The second flow rate balancer 26 b is provided in the second refrigerant path (flow rate-variable refrigerant path) 23 b at the four-way valve 22 side. The third flow rate balancer 26 c is provided in the third refrigerant path (flow rate-variable refrigerant path) 23 c at the four-way valve 22 side. As described above, the first refrigerant path 23 a to the third refrigerant path 23 c are the refrigerant paths with the first flow rate balancers 26 a to the third flow rate balancer 26 c, respectively.

In this embodiment, the first flow rate balancer 26 a, the second flow rate balancer 26 b, and the third flow rate balancer 26 c are the same in configuration. Accordingly, only the first flow rate balancer 26 a will be described below and descriptions of the second flow rate balancer 26 b and the third flow rate balancer 26 c will be omitted. In FIG. 1A, the members of the second flow rate balancer 26 b corresponding to the members of the first flow rate balancer 26 a are given the reference numerals given to the members of the first flow rate balancer 26 a in which the last symbol a is replaced with b. Similarly, the members of the third flow rate balancer 26 c corresponding to the members of the first flow rate balancer 26 a are given the reference numerals given to the members of the first flow rate balancer 26 a in which the last symbol a is replaced with c.

The first flow rate balancer 26 a has a capillary tube 26 aa as a flow rate regulator with a predetermined flow passage resistance, an open/close valve 26 ab as an open/close device, and a bypass pipe 26 ac. The capillary tube 26 aa regulates the amount of the refrigerant flowing through the first refrigerant path 23 a. That is, the capillary tube 26 aa decreases the amount of the refrigerant flowing through the first refrigerant path 23 a to be smaller than the amount of the refrigerant flowing through each of the fourth refrigerant path 23 d to the seventh refrigerant path 23 g without flow rate balancers. The bypass pipe 26 ac is coupled to the first refrigerant path 23 a bypassing the capillary tube 26 aa. The open/close valve 26 ab is provided in the bypass pipe 26 ac. When being opened, the open/close valve 26 ab allows passage of the refrigerant in the bypass pipe 26 ac. When being closed, the open/close valve 26 ab shuts off the passage of the refrigerant in the bypass pipe 26 ac. Therefore, when the open/close valve 26 ab is opened, the refrigerant flows into the bypass pipe 26 ac bypassing the capillary tube 26 aa. Accordingly, the flow rate of the refrigerant is not regulated by the capillary tube 26 aa. When the open/close valve 26 ab is closed, the refrigerant does not flow into the bypass pipe 26 ac but flows through the capillary tube 26 aa. As a result, the flow rate of the refrigerant is regulated by the capillary tube 26 aa.

The outdoor fan 29 is a propeller fan made from a resin material and is disposed in the vicinity of the outdoor heat exchanger 23. The outdoor fan 29 is rotated by a fan motor not illustrated. Accordingly, the ambient air is taken into the outdoor unit 2 from an inlet not illustrated provided in the outdoor unit 2. Further, the ambient air having undergone heat exchange with the refrigerant flowing through the first refrigerant path 23 a to the seventh refrigerant path 23 g in the outdoor heat exchanger 23 is released to the outside of the outdoor unit 2 from an outlet not illustrated provided in the outdoor unit 2.

Besides the members described above, the outdoor unit 2 is provided with various sensors. As illustrated in FIG. 1A, the discharge pipe 41 is provided with a high-pressure sensor 31 and a discharge temperature sensor 33. The high-pressure sensor 31 detects the pressure of the refrigerant discharged from the compressor 21. The discharge temperature sensor 33 detects the temperature of the refrigerant discharged from the compressor 21. The refrigerant pipe 46 is provided with a low-pressure sensor 32 and an intake temperature sensor 34 in the vicinity of the refrigerant inflow side of the accumulator 25. The low-pressure sensor 32 detects the pressure of the refrigerant taken into the compressor 21. The intake temperature sensor 34 detects the temperature of the refrigerant taken into the compressor 21.

The outdoor heat exchanger 23 is provided with an outdoor heat exchange temperature sensor 35 that detects the temperature of the outdoor heat exchanger 23. The outdoor unit liquid pipe 44 is provided with a refrigerant temperature sensor 36 that detects the temperature of the refrigerant flowing into the outdoor heat exchanger 23 or the refrigerant flowing out of the outdoor heat exchanger 23. In addition, the outdoor unit 2 is provided with an ambient air temperature sensor 37 as an ambient air temperature detector detecting the temperature of the outdoor flowing into the outdoor unit 2, that is, the ambient air temperature, in the vicinity of the inlet not illustrated of the outdoor unit 2.

The outdoor unit 2 is also provided with the outdoor unit controller 200. The outdoor unit controller 200 is mounted on a control substrate stored in an electrical equipment box not illustrated of the outdoor unit 2. The outdoor unit 2 includes a CPU 210, a storage unit 220, a communication unit 230, and a sensor input unit 240 as illustrated in FIG. 1B. The CPU 210 is a controller of the outdoor unit 2.

The storage unit 220 includes a ROM and a RAM. The storage unit 220 stores control programs for the outdoor unit 2, the detection values corresponding to detection signals from the various sensors, the driving states of the compressor 21 and the outdoor fan 29, and others. The communication unit 230 is an interface that communicates with the indoor units 5 a to 5 c. The sensor input unit 240 obtains the results of detection by the various sensors of the outdoor unit 2 to output the same to the CPU 210. The detection values (detection results) from the various sensors are input into the CPU 210 via the sensor input unit 240. In addition, operation start/stop signals transmitted from the indoor units 5 a to 5 c and operation information signals including operation information (setting temperature, indoor temperature, and others) are input into the CPU 210 via the communication unit 230. The CPU 210 controls, on the basis of the various kinds of input information, the degree of opening of each of the first expansion valve 24 a to the third expansion valve 24 c, the driving of the compressor 21 and the outdoor fan 29, and the opening/closing of the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c.

Next, the three indoor units 5 a to 5 c will be described. The three indoor units 5 a to 5 c include indoor heat exchangers 51 a to 51 c, liquid pipe coupling portions 53 a to 53 c, gas pipe coupling portions 54 a to 54 c, and indoor fans 55 a to 55 c, respectively. The indoor heat exchangers 51 a to 51 c are coupled respectively with the liquid pipe coupling portions 53 a to 53 c and the gas pipe coupling portions 54 a to 54 c via refrigerant pipes described later in detail to constitute indoor unit refrigerant circuits 50 a to 50 c as part of the refrigerant circuit 10 respectively.

The indoor units 5 a to 5 c are the same in configuration. Accordingly, only the configuration of the indoor unit 5 a will be described below and descriptions of the other indoor units 5 b and 5 c will be omitted. In FIG. 1A, the members of the indoor unit 5 b corresponding to the members of the indoor unit 5 a are given the reference numerals given to the members of the indoor unit 5 a in which the last symbol a is replaced with b. Similarly, the members of the indoor unit 5 c corresponding to the members of the indoor unit 5 a are given the reference numerals given to the members of the indoor unit 5 a in which the last symbol a is replaced with c.

The indoor heat exchanger 51 a exchanges heat between the refrigerant and the indoor air taken into the indoor unit 5 a from the suction opening not illustrated included in the indoor unit 5 a by the rotation of the indoor fan 55 a described later. One of refrigerant entry/exit openings of the indoor heat exchanger 51 a is coupled to the liquid pipe coupling portion 53 a via an indoor unit liquid pipe 71 a. The other refrigerant entry/exit opening of the indoor heat exchanger 51 a is coupled to the gas pipe coupling portion 54 a via an indoor unit gas pipe 72 a. The refrigerant pipes are coupled to the liquid pipe coupling portion 53 a and the gas pipe coupling portion 54 a by welding or with flare nuts or the like. The indoor heat exchanger 51 a serves as an evaporator when the indoor unit 5 a performs cooling operation, and serves as a condenser when the indoor unit 5 a performs heating operation.

The indoor fan 55 a is a cross-flow fan made from a resin material and is disposed in the vicinity of the indoor heat exchanger 51 a. The indoor fan 55 a is rotated by a fan motor not illustrated. Accordingly, the indoor air is taken into the indoor unit 5 a from a suction opening not illustrated. Further, the indoor air having undergone heat exchange with the refrigerant in the indoor heat exchanger 51 a is supplied to the room from a blow opening not illustrated included in the indoor unit 5 a.

Besides the members described above, the indoor unit 5 a is provided with various sensors. The indoor unit liquid pipe 71 a is provided with a liquid-side temperature sensor 61 a. The liquid-side temperature sensor 61 a detects the temperature of the refrigerant flowing into the indoor heat exchanger 51 a or the refrigerant flowing out of the indoor heat exchanger 51 a. The indoor unit gas pipe 72 a is provided with a gas-side temperature sensor 62 a. The gas-side temperature sensor 62 a detects the temperature of the refrigerant flowing out of the indoor heat exchanger 51 a or the refrigerant flowing into the indoor heat exchanger 51 a. The indoor unit 5 a is provided with an indoor temperature sensor 63 a in the vicinity of a suction opening. The indoor temperature sensor 63 a detects the temperature of the indoor air flowing into the indoor unit 5 a (that is, the indoor temperature).

Next, the flow of the refrigerant in the refrigerant circuit 10 and the operations of the members when the air conditioner 1 of this embodiment performs heating operation will be described with reference to FIGS. 1A, 2A, and 2B. In the air conditioner 1 of this embodiment, the opening/closing state of each of the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c vary depending on whether the ambient air temperature detected by the ambient air temperature sensor 37 is equal to or higher than a threshold ambient air temperature (for example, −15° C.) or the ambient air temperature is lower than the threshold ambient air temperature. The threshold ambient air temperature is as described below. That is, when the ambient air temperature is lower than the threshold ambient air temperature, the heating capacity of the air conditioner 1 decreases significantly due to reduction in the circulation volume of refrigerant. The threshold ambient air temperature is determined (confirmed) in advance by experiments or the like.

Hereinafter, descriptions will be first given as to the flow of the refrigerant in the refrigerant circuit 10 and the operations of the members in the case where the ambient air temperature detected by the ambient air temperature sensor 37 is equal to or higher than the threshold ambient air temperature. Then, descriptions will be given as to the flow of the refrigerant in the refrigerant circuit 10 and the operations of the members in the case where the ambient air temperature detected by the ambient air temperature sensor 37 is lower than the threshold ambient air temperature.

The following descriptions are based on the assumption that the indoor units 5 a to 5 c perform heating operation. The detailed descriptions of the case where the indoor units 5 a to 5 c perform cooling operation or dehumidifying operation will be omitted. In addition, the arrows in FIG. 1A indicate the flow of the refrigerant. Further, FIGS. 2A and 2B illustrate the opened open/close valves 26 ab to 26 cb in a void shape, and illustrate the closed open/close valves 26 ab to 26 cb in a solid filled shape.

<The Case where the Ambient Air Temperature is Equal to or Higher than the Threshold Ambient Air Temperature>

As illustrated in FIG. 1A, when the indoor units 5 a to 5 c perform heating operation, that is, when the refrigerant circuit 10 is in the heating cycle, the CPU 210 of the outdoor unit controller 200 switches the four-way valve 22 such that the ports a and d of the four-way valve 22 communicate with each other and the ports b and c of the same communicate with each other as shown by solid lines in FIG. 1A. Accordingly, the outdoor heat exchanger 23 serves as an evaporator and the indoor heat exchangers 51 a to 51 c serve as condensers. The CPU 210 activates the compressor 21 and the outdoor fan 29. The CPU 210 further controls the opening/closing of each of the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c. In this example, the ambient air temperature obtained from the ambient air temperature sensor 37 is equal to or higher than the threshold ambient air temperature. Accordingly, the CPU 210 closes the open/close valves 26 ab to 26 cb as illustrated in FIG. 2A.

The high-pressure refrigerant discharged from the compressor 21 flows from the discharge pipe 41 into the four-way valve 22. Further, the refrigerant flows from the four-way valve 22 through the outdoor unit gas pipe 45 and enters into the gas pipe 9 via the gas-side closing valve 28. The refrigerant having flown into the gas pipe 9 then branches and enters into the indoor units 5 a to 5 c via the gas pipe coupling portions 54 a to 54 c. The refrigerant having flown into the indoor units 5 a to 5 c then flows through the indoor unit gas pipes 72 a to 72 c and enters into the indoor heat exchangers 51 a to 51 c respectively. The refrigerant is condensed through heat exchange with the indoor air taken into the indoor units 5 a to 5 c by the rotation of the indoor fans 55 a to 55 c. In this manner, the indoor heat exchangers 51 a to 51 c serve as condensers to blow the indoor air having undergone heat exchange with the refrigerant in the indoor heat exchangers 51 a to 51 c into the room from blow openings not illustrated. Accordingly, the room with the indoor units 5 a to 5 c is heated.

The refrigerant having flown out of the indoor heat exchangers 51 a to 51 c flows through the respective indoor unit liquid pipes 71 a to 71 c and enters into the respective first liquid pipe 8 a to third liquid pipe 8 c via the respective liquid pipe coupling portions 53 a to 53 c. The refrigerant having flown into the first liquid pipe 8 a to the third liquid pipe 8 c enters into the outdoor unit 2 via the respective first liquid-side closing valve 27 a to third liquid-side closing valve 27 c. After that, the refrigerant is decompressed when passing through each of the first expansion valve 24 a to the third expansion valve 24 c while flowing through each of the first liquid branch pipe 44 a to the third liquid branch pipe 44 c.

The refrigerant decompressed by each of the expansion valves flows from each of the first liquid branch pipe 44 a to the third liquid branch pipe 44 c into the outdoor unit liquid pipe 44 and joins together. Then, the refrigerant flows into the outdoor heat exchanger 23 and branches to the first refrigerant path 23 a to the seventh refrigerant path 23 g. The refrigerant having entered into the outdoor heat exchanger 23 and flown through each of the first refrigerant path 23 a to the seventh refrigerant path 23 g is evaporated through heat exchange with the ambient air taken into the outdoor unit 2 by the rotation of the outdoor fan 29.

When the refrigerant flows through each of the first refrigerant path 23 a to the seventh refrigerant path 23 g, each of the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c of the respective first refrigerant path 23 a to third refrigerant path 23 c is closed as illustrated in FIG. 2A. Accordingly, the refrigerant having entered into each of the first flow rate balancer 26 a to the third flow rate balancer 26 c flows through the capillary tubes 26 aa to 26 ca respectively.

Accordingly, the amount of the refrigerant flowing through each of the first refrigerant path 23 a to the third refrigerant path 23 c is regulated by the flow passage resistance in each of the respective capillary tubes 26 aa to 26 ca, and is lower than the amount of the refrigerant flowing through each of the other refrigerant paths (the fourth refrigerant path 23 d to the seventh refrigerant path 23 g) without the flow rate balancer. Therefore, even when the refrigerant in the gas-liquid two-phase state or in the liquid state enters into the outdoor heat exchanger 23, it is possible to prevent the situation in which the liquid refrigerant flows biased toward the lower refrigerant paths (in this example, the first refrigerant path 23 a to the third refrigerant path 23 c) under the influence of gravity. In this manner, the flow of the refrigerant in the outdoor heat exchanger 23 is unlikely to be biased toward the lower refrigerant paths. This suppresses the degradation in evaporating performance of the outdoor heat exchanger 23. As a result, it is possible to ensure sufficient heating capacity.

The refrigerant having flown out of the refrigerant pipe 43 from each of the first refrigerant path 23 a to the seventh refrigerant path 23 g of the outdoor heat exchanger 23 flows through the refrigerant pipe 46 and enters into the accumulator 25 via the four-way valve 22. After that, the refrigerant is divided by the accumulator 25 into a gas refrigerant and a liquid refrigerant. The gas refrigerant having flown out of the accumulator 25 flows through the intake pipe 42 to be sucked into the compressor 21 and compressed again there.

<The Case where the Ambient Air Temperature is Lower than the Threshold Ambient Air Temperature>

When the ambient air temperature detected by the ambient air temperature sensor 37 is lower than the threshold ambient air temperature, the flowing of the refrigerant and the operations of the refrigerant circuit 10 except for the flowing of the refrigerant and the operations related to the opening/closing control of the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c, are the same as those in the foregoing case where the ambient air temperature is equal to or higher than the threshold ambient air temperature, and therefore descriptions thereof will be omitted. Hereinafter, the flow of the refrigerant in each of the first flow rate balancer 26 a to the third flow rate balancer 26 c and its effect will be described.

In this case, the ambient air temperature obtained from the ambient air temperature sensor 37 is lower than the threshold ambient air temperature. Accordingly, as illustrated in FIG. 2B, the CPU 210 opens the open/close valves 26 ab to 26 cb. In this state, when the refrigerant flows through each of the refrigerant paths of the outdoor heat exchanger 23, the refrigerant having entered into each of the first flow rate balancer 26 a to the third flow rate balancer 26 c does not flow through each of the respective capillary tubes 26 aa to 26 ca but flows through each of the respective bypass pipe 26 ac to 26 cc as illustrated in FIG. 2B. Accordingly, the amount of the refrigerant flowing through each of the first refrigerant path 23 a to the third refrigerant path 23 c is not regulated. Thus, the amount of the refrigerant flowing through each of the first flow rate balancer 26 a to the third flow rate balancer 26 c is unlikely to decrease. Therefore, it is possible to suppress reduction in the circulation volume of the refrigerant in the refrigerant circuit 10. As a result, it is possible to suppress degradation in heating capacity resulting from the reduction in the circulation volume of the refrigerant.

Next, the process performed by the CPU 210 of the outdoor unit controller 200 when the air conditioner 1 according to this embodiment performs heating operation will be described with reference to the flowchart of FIG. 3. In the flowchart of FIG. 3, the symbol ST indicates the steps in the process and the numbers following the symbol ST indicate the step numbers. FIG. 3 describes the process mainly related to control on the circulation volume of the refrigerant depending on the ambient air temperature. Descriptions of other processes, for example, general processes related to the air conditioner 1 such as controls under operating conditions specified by the user when heating operation is performed will be omitted.

First, the CPU 210 determines whether the operating instruction from the user is an instruction for heating operation (ST1). When the instruction is not an instruction for heating operation (ST1-No), the CPU 210 controls cooling operation or dehumidifying operation (ST12), and then returns the process to ST1. The control of cooling operation or dehumidifying operation means a general control during cooling operation or dehumidifying operation. For example, the CPU 210 operates the four-way valve 22 to switch a refrigerant circuit 10 such that the outdoor heat exchanger 23 serves as a condenser and the indoor heat exchangers 51 a to 51 c serve as evaporators. The CPU 210 also activates the compressor 21 and the outdoor fan 29 at the rotation speed according to the performance required by the indoor units 5 a to 5 c during cooling operation or dehumidifying operation.

When determining that the instruction from the user is an instruction for heating operation (ST1-Yes), the CPU 210 makes preparations for heating operation (ST2). At the preparations for heating operation, the CPU 210 operates the four-way valve 22 to switch the refrigerant circuit 10 such that the outdoor heat exchanger 23 serves as an evaporator and the indoor heat exchangers 51 a to 51 c serve as condensers. That is, the CPU 210 brings the refrigerant circuit 10 into the state illustrated in FIG. 1A.

Next, the CPU 210 activates the compressor 21 and the outdoor fan 29 (ST3). Specifically, the CPU 210 activates the compressor 21 and the outdoor fan 29 at the rotation speed according to the performance required by the indoor units 5 a to 5 c.

Next, the CPU 210 obtains the ambient air temperature detected by the ambient air temperature sensor 37 via the sensor input unit 240 (ST4). The CPU 210 stores the obtained ambient air temperature in the storage unit 220.

Next, the CPU 210 determines whether the obtained ambient air temperature is lower than the threshold ambient air temperature (ST5). When the obtained ambient air temperature is lower than the threshold ambient air temperature (ST5-Yes), the CPU 210 opens the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c (ST6), and then moves the process to ST8.

When determining at ST5 that the obtained ambient air temperature is not lower than the threshold ambient air temperature (ST5-No), the CPU 210 closes the open/close valves 26 ab to 26 cb of the respective first flow rate balancer 26 a to third flow rate balancer 26 c (ST7), and then moves the process to ST8.

After ST6 or ST7, the CPU 210 performs a heating operation control (ST8). At the heating operation control, the CPU 210 receives via the communication unit 230 an operation information signal including operation information (setting temperature, indoor temperature, and others) transmitted from the indoor units 5 a to 5 c. The CPU 210 further controls the driving of the compressor 21 and the outdoor fan 29 and the degree of opening of each of the first expansion valve 24 a to the third expansion valve 24 c on the basis of the operation information signal.

Next, the CPU 210 determines whether there is an instruction for switching operation from the user (ST9). The instruction for switching operation is an instruction for switching from the current operation to another operation, for example, switching from heating operation to cooling operation or dehumidifying operation. When there is an instruction for switching operation (ST9-Yes), the CPU 210 returns the process to ST1.

When there is no instruction for switching operation (ST9-No), the CPU 210 determines whether there is an instruction for stopping operation (ST10). The instruction for stopping operation is an instruction for stopping the operation of each of the indoor units 5 a to 5 c.

When there is no instruction for stopping operation (ST10-No), the CPU 210 returns the process to ST4. When there is an instruction for stopping operation (ST10-Yes), the CPU 210 performs an operation stopping process (ST11), and terminates the process. At the operation stopping process, the CPU 210 stops the compressor 21 and the outdoor fan 29.

As described above, at the air conditioner 1 in this embodiment, when the outdoor heat exchanger 23 serves as an evaporator, that is, when the air conditioner 1 performs heating operation, the CPU 210 opens each of the open/close valves 26 ab to 26 cb so as not to regulate the amount of the refrigerant flowing through each of the first refrigerant path 23 a to third refrigerant path 23 c in the case where the ambient air temperature detected by the ambient air temperature sensor 37 is lower than the predetermined threshold ambient air temperature. In contrast, in the case where the ambient air temperature detected by the ambient air temperature sensor 37 is equal to or higher than the predetermined threshold ambient temperature, the CPU 210 closes each of the open/close valves 26 ab to 26 cb to regulate the amount of the refrigerant flowing through each of the first refrigerant path 23 a to third refrigerant path 23 c. Accordingly, it is possible to suppress degradation in heating capacity resulting from reduction in the circulation volume of the refrigerant at lower ambient air temperatures while correcting the bias of the flow rate of refrigerant among the refrigerant paths.

The CPU 210 may regulate to some extent the amount of the refrigerant flowing through each of the first refrigerant path 23 a to the third refrigerant path 23 c even in the case where the ambient air temperature detected by the ambient air temperature sensor 37 is equal to or higher than the threshold ambient air temperature. Accordingly, in the case where the ambient air temperature is equal to or higher than the threshold ambient air temperature, the CPU 210 decreases the amount of the refrigerant flowing through each of the first refrigerant path 23 a to the third refrigerant path 23 c as compared to the case where the ambient air temperature is lower than the threshold ambient air temperature. In this case, when the ambient air temperature is equal to or higher than the threshold ambient air temperature, the CPU 210 may adjust the amount of the refrigerant flowing through each of the first refrigerant path 23 a to the third refrigerant path 23 c to be equal to or lower than (or almost the same as) the amount of the refrigerant flowing through each of the fourth refrigerant path 23 d to the seventh refrigerant path 23 g. This adjustment can be made by use of flow rate adjustment valves described later, for example.

In the embodiment described above, the first flow rate balancer 26 a to the third flow rate balancer 26 c have the capillary tubes 26 aa to 26 ca, the open/close valves 26 ab to 26 cb, and the bypass pipes 26 ac to 26 cc respectively. Instead of this, the first flow rate balancer 26 a to the third flow rate balancer 26 c may be flow rate adjustment valves (for example, electronic expansion valves). In this case, when the ambient air temperature is lower than the threshold ambient air temperature, the CPU 210 may open fully the flow rate adjustment valves, for example. When the ambient air temperature is equal to or higher than the threshold ambient air temperature, the CPU 210 may set the degree of opening of each flow rate adjustment valve to a predetermined value. For example, the CPU 210 may adjust the degree of opening of the flow rate adjustment valve such that the amount of the refrigerant flowing through the refrigerant path provided with the flow rate adjustment valve are equal to or lower than (or almost the same as) the amount of the refrigerant flowing through the refrigerant path not provided with the flow rate balancer.

In this embodiment, the capillary tubes 26 aa to 26 ca of the respective first flow rate balancer 26 a to third flow rate balancer 26 c have the same flow passage resistance. Instead of this, the flow passage resistance of the capillary tube 26 aa included in the lowest first refrigerant path 23 a may be higher than the flow passage resistance of each of the other capillary tubes 26 ba and 26 ca. In this manner, by making uneven the flow passage resistances of the capillary tubes 26 aa to 26 ca (for example, setting the flow passage resistances to be different from one another), the regulated flow rates of the refrigerant in the refrigerant paths may be made uneven (for example, made different from each other). That is, the flow passage resistances of the capillary tubes 26 aa to 26 ca may be selected such that the regulated flow rates of the refrigerant flowing through the first refrigerant path 23 a to the third refrigerant path 23 c become uneven.

When the first flow rate balancer 26 a to the third flow rate balancer 26 c are flow rate adjustment valves (expansion valves), the CPU 210 may set the degree of opening of the flow rate adjustment valve included in the lowest first refrigerant path 23 a to be smaller than the degree of opening of each of the other flow rate adjustment valves. In this manner, the CPU 210 may make uneven the degrees of opening of the flow rate adjustment valves to make uneven the regulated flow rates of the refrigerant flowing through the refrigerant paths. That is, the CPU 210 may control the degrees of opening of the flow rate adjustment valves such that the regulated flow rates of the refrigerant flowing through the first refrigerant path 23 a to the third refrigerant path 23 c become uneven.

In this embodiment, the flow rate balancer is included in each of the first refrigerant path 23 a to the third refrigerant path 23 c. The flow rate balancer may be included in at least the lowest first refrigerant path 23 a out of the refrigerant paths vertically disposed in parallel.

The first refrigerant path 23 a to the third refrigerant path 23 c may be the same in structure as the fourth refrigerant path 23 d to the seventh refrigerant path 23 g except for including the respective first flow rate balancer 26 a to third flow rate balancer 26 c.

The first refrigerant path 23 a to the third refrigerant path 23 c do not necessarily have to include the first flow rate balancer 26 a to the third flow rate balancer 26 c. The first refrigerant path 23 a to the third refrigerant path 23 c merely need to be flow rate-variable refrigerant paths structured to be capable of being regulated in flow rate by the CPU 210. The flow rate-variable refrigerant path may be disposed in at least the lowest one of the refrigerant paths vertically disposed in parallel.

The air conditioner according to the embodiment of the present disclosure may be any one of the following first to fifth air conditioners.

The first air conditioner is an air conditioner having an outdoor heat exchanger with a plurality of refrigerant paths and an ambient air temperature detection unit detecting the ambient air temperature. At least one of the plurality of refrigerant paths has a flow rate balancing unit that switches operations on whether or not to regulate the flow rate of a refrigerant flowing through the refrigerant path. When the outdoor heat exchanger serves as an evaporator, the flow rate balancing unit does not regulate the flow rate of the refrigerant in the case where the ambient air temperature detected by the ambient air temperature detection unit is lower than a predetermined threshold ambient air temperature. When the outdoor heat exchanger serves as an evaporator, the flow rate balancing unit regulates the flow rate of the refrigerant in the case where the ambient air temperature detected by the ambient air temperature detection unit is higher than the threshold ambient air temperature.

In the second air conditioner according to the first air conditioner, the flow rate balancing unit has a flow rate regulation unit that regulates the flow rate of the refrigerant flowing through the refrigerant path with the flow rate balancing unit and a bypass pipe that includes an open/close unit and bypasses the flow rate regulation unit. When the outdoor heat exchanger serves as an evaporator, the open/close unit is opened in the case where the ambient air temperature detected by the ambient air temperature detection unit is lower than the threshold ambient air temperature. When the outdoor heat exchanger serves as an evaporator, the open/close unit is closed in the case where when the ambient air temperature detected by the ambient air temperature detection unit is equal to or higher than the threshold ambient air temperature.

In the third air conditioner according to the first or second air conditioner, when the flow rate balancing unit is provided in a plurality of refrigerant paths, the flow rate regulation unit is selected such that the regulated flow rates of the refrigerant are different among the plurality of paths.

In the fourth air conditioner according to the first air conditioner, the flow rate balancing unit is composed of a flow rate adjustment valve. When the outdoor heat exchanger serves as an evaporator, the flow rate adjustment valve is fully opened in the case where the ambient air temperature detected by the ambient air temperature detection unit is lower than the threshold ambient air temperature. When the outdoor heat exchanger serves as an evaporator, the flow rate adjustment valve is opened at a predetermined degree in the case where the ambient air temperature detected by the ambient air temperature detection unit is equal to or higher than the threshold ambient air temperature. When the flow rate balancing unit is provided in a plurality of refrigerant paths, the degree of opening of the flow rate adjustment valve is controlled such that the regulated flow rates of the refrigerant are different among the plurality of paths.

In the fifth air conditioner according to the first to fourth air conditioners, the outdoor heat exchanger has the plurality of refrigerant paths vertically disposed in parallel and the flow rate balancing unit provided in at least the lowest refrigerant path.

The foregoing detailed description has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is not intended to be exhaustive or to limit the subject matter described herein to the precise form disclosed. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims appended hereto. 

What is claimed is:
 1. An outdoor unit of an air conditioner, comprising: an outdoor heat exchanger provided with a plurality of refrigerant paths including a flow rate-variable refrigerant path; an ambient air temperature detector that detects an ambient air temperature; and a controller that decreases a flow rate of a refrigerant flowing into the flow rate-variable refrigerant path in a case where the ambient air temperature detected by the ambient air temperature detector is equal to or higher than a threshold ambient air temperature as compared to a case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.
 2. The outdoor unit of the air conditioner according to claim 1, wherein the controller regulates the flow rate of the refrigerant flowing into the flow rate-variable refrigerant path in the case where the ambient air temperature is equal to or higher than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator, and the controller does not regulate the flow rate of the refrigerant flowing into the flow rate-variable refrigerant path in the case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.
 3. The outdoor unit of the air conditioner according to claim 1, wherein the flow rate-variable refrigerant path is the refrigerant path with a flow rate balancer, and the controller uses the flow rate balancer to regulate the flow rate of the refrigerant flowing into the flow rate-variable refrigerant path.
 4. The outdoor unit of the air conditioner according to claim 3, wherein the flow rate balancer includes a flow rate regulator that regulates the flow rate of the refrigerant flowing into the flow rate-variable refrigerant path, a bypass pipe that bypasses the flow rate regulator, and an open/close device that allows passage of the refrigerant through the bypass pipe when being opened and that shuts off the passage of the refrigerant through the bypass pipe when being closed, the controller opens the open/close device in the case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator, and the controller closes the open/close device in the case where the ambient air temperature is equal to or higher than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.
 5. The outdoor unit of the air conditioner according to claim 4, comprising a plurality of the flow rate-variable refrigerant paths, wherein flow passage resistance of the flow rate regulator of the flow rate balancer included in each of the flow rate-variable refrigerant paths is selected such that the regulated amount of the flow rate of the refrigerant flowing into each of the plurality of flow rate-variable refrigerant paths becomes uneven.
 6. The outdoor unit of the air conditioner according to claim 3, wherein the flow rate balancer is a flow rate adjustment valve, the controller fully opens the flow rate adjustment valve in the case where the ambient air temperature is lower than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator, and the controller sets the degree of opening of the flow rate adjustment valve to a predetermined value in the case where the ambient air temperature is equal to or higher than the threshold ambient air temperature, when the outdoor heat exchanger serves as an evaporator.
 7. The outdoor unit of the air conditioner according to claim 6, comprising a plurality of the flow rate-variable refrigerant paths, wherein the controller controls the degree of opening of the flow rate adjustment valve such that the regulated amount of the flow rate of the refrigerant flowing into each of the plurality of flow rate-variable refrigerant paths becomes uneven.
 8. The outdoor unit of an air conditioner according to claim 1, wherein in the outdoor heat exchanger, the plurality of refrigerant paths is disposed vertically in parallel, the flow rate-variable refrigerant path being disposed in at least the bottom of the plurality of refrigerant paths.
 9. An air conditioner comprising: the outdoor unit according to claim 1; an indoor unit; and a pipe that couples the outdoor unit and the indoor unit. 